A knocker so mysterious and suspicious that Policeman X 37, first coming upon it, felt inclined to take it instantly in custody, but compromised with his professional instincts by sharply and sternly noting it with an eye that admitted of no nonsense, but confidently expected to detect its secret yet.

An ugly knocker; a knocker with a hard, human face, that was a type of the harder human face within.

A human face that held between its teeth a brazen rod.

So hereafter, in the mysterious future should be held, etc., etc.
But if the knocker had a fierce human aspect in the glare of day, you should have seen it at night, when it peered out of the gathering shadows and suggested an ambushed figure; when the light of the street lamps fell upon it, and wrought a play of sinister expression in its hard outlines; when it seemed to wink meaningly at a shrouded figure who, as the night fell darkly, crept up the steps and passed into the mysterious house; when the swinging door disclosed a black passage into which the figure seemed to lose itself and become a part of the mysterious gloom; when the night grew boisterous and the fierce wind made furious charges at the knocker, as if to wrench it off and carry it away in triumph.

Such a night as this.
It was a wild and pitiless wind.